The Card and The Test

The Radeon HD 4830 reference board we tested is based on a revised design put together for this part, but AMD built this chip to be able to fit into existing 4850 board designs as well. The maximum power envelope is the same, but actual power usage will be lower. AMD has informed us that initial boards based on the 4830 will be using 4850 boards, but that down the line we should start seeing boards based on the more compact 4830 reference design.

As for how the GPU stacks up against some of the other offerings from AMD, here's a handy chart:

ATI Radeon HD 4870

ATI Radeon HD 4850

ATI Radeon HD 4830

ATI Radeon HD 4670

Stream Processors

800

800

640

320

Texture Units

40

40

32

32

ROPs

16

16

16

8

Core Clock

750MHz

625MHz

575MHz

750MHz

Memory Clock

900MHz (3600MHz data rate) GDDR5

993MHz (1986MHz data rate) GDDR3

900MHz (1800MHz data rate) GDDR3

1000MHz (2000MHz data rate) GDDR3

Memory Bus Width

256-bit

256-bit

256-bit

128-bit

Frame Buffer

512MB/1GB

512MB

512MB

512MB

Transistor Count

956M

956M

956M

514M

Manufacturing Process

TSMC 55nm

TSMC 55nm

TSMC 55nm

TSMC 55nm

Based on the information we know about the GPU, the 4830 is clearly just an RV770 with two SIMDs disabled. While AMD does have safeguards built into their GPUs to help improve yield, nothing is perfect. There will be ICs that come off the line that simply can't function properly at the desired speed or with all the hardware enabled to make it onto a higher end card. Chip makers will save these parts and bin them for possible use in lower end products later. We also sometimes see higher end binned chips released as special editions overclocked models, so it does work both ways.

The price of the 4830 means that it will see higher volume sales than either the 4850 or the 4870. That's just how it works: more people buy cheaper parts. The interesting twist here is that the RV770 is being used in 3 different parts ranging from $130 to $300 with very little time lapse between the initial release and the current situation.

While we still would really love to see a top to bottom launch on day one of a new architecture some time, this is very impressive in it's own right. The delay between the launch of the 4870 and the 4830 is likely due to the fact that AMD needed to maintain enough supply to meet demand for it's two higher end parts while steadily building up a supply of chips for use in the 4830. As demand will be higher, stockpiling chips that can't run at 4830 specification for a few months will certainly help meet the needs of the market.

Now that we know what we're testing, let's take a look at our test platform.

And I think I found my next video card upgrade. Have been either waiting for the 4850 to drop a bit more, or something to come out between the 4670 and 4850 to come out, and this one hits exactly where I figured it would. Nipping at the heels of the 9800gtx in a few benchies there, and at the Res that matters for me 1680x1050. This looks like something I can pair with my 3870 toxic edition till I can afford a full on 4850 or 4870. Then if I wanted to I can get rid of the 3870 and run Xfire with the 4830 and 4850. Reply

I had no idea that different chipsets (or mobos) and cpus could result in such a dramatic difference in power consumption. I sure want my computer to consume as little as possible when I am not using it.

More importantly, all your previous reviews show roughly a 40+ idle and load watt difference between the 4850 and 4870, yet this review has it down to 3-4 watts at both. Was there a problem with 4870 power consumption that has now been fixed? Reply

And now these 4850 and 4870 numbers show a wider margin again. With a different testbed I'd expect different numbers, but the relative difference on the same testbed should be the same. These numbers are more in line with AT's other 4850/70 power numbers. The original article's numbers need to be explained. Reply